Remote displacement on Ansys Mechanical APDL

- April 17, 2019 at 4:38 pm
  
  marcocesari
  Subscriber
  
  Hi, i would to konw how apply remote displacement on surface in relation to a point. In particular i try to fix all traslation of a surface in relation to a point but i want that this surface have free rotation in relation with this point. In other words i would apply an spherical joint on my body in Ansys Mechanical APDL.
  
  Thanks, Marco Cesari
- April 17, 2019 at 7:46 pm
  Sandeep Medikonda
  Ansys Employee
  You can select the point, create a named selection (say P1) and use the d command to constrain each degree of freedom.
```
CM,P1,KP
d,P1,ux,%_fix%
...
```
  You can read more about them in the manual.
  
  Link1
  
  Link2
- April 18, 2019 at 7:41 am
  
  marcocesari
  Subscriber
  
  It's not possible to use keypoint and surface in the command 'CM' that you have linked, so how can i relate keypoint and surface?
  
  If i'm not wrong in this way i create an named selection with the keyopoint, but don't relate the keypoint with surface of my body. My idea is to relate point and the surface of my body constraining only traslational degree of freedom between the surface and keypoint and then fix the point in the absolute coordinate system. In this way i would constrain only traslational degree of freedom of my surface compared to keypoint and would have free the rotational degree of freedom
  
  thanks
- April 18, 2019 at 10:44 am
  jj77
  Subscriber
  Ok - you can use constraint equations typlically for this.
  
  CERIG (constraint equations of rigid type - one can choose to use only transnational dof) is one option making the surface stiff where the remote point connects to (think one needs to have a mass21 element on that remote point/node attached, but you can set the mass to almost zero 1E-10 kg or something)
  
  If you do not want to add stiffness, then there is RBE3 which is for applying remote loads to a surface/edge and that does not add stiffness.
  
  (attached is an example of RBE3 where a central node (nr 3) is connected to the edge of a shell mesh - taken from ansys help
```
7.16. Example: Quasi-Static Analysis of a Multi-Rotor System
```
  )
  
  Finally one can use more general MPC type.
  
  Search all this and you will get loads of info on the internet (I have not used these commands for many years but they should still work).
  
  Also this pdf is good:
  
  http://www.padtinc.com/blog/wp-content/uploads/sites/2/sites/2/oldblog/PADT-Webinar-ConstraintEquations-2012_04_27.pdf